From 9e1515d14434c93c612e20b7fdd81131cb16a55f Mon Sep 17 00:00:00 2001
From: Daniel Correia <daniel.correia@sky.uk>
Date: Thu, 14 Sep 2023 08:16:42 +0100
Subject: [PATCH] Add support for constant attributes. Update example to
 reflect changes.

---
 examples/examples/hyper.rs       |  8 +++++++-
 tracing-logstash/src/logstash.rs | 13 +++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/examples/examples/hyper.rs b/examples/examples/hyper.rs
index f741450..a0ae36f 100644
--- a/examples/examples/hyper.rs
+++ b/examples/examples/hyper.rs
@@ -24,7 +24,13 @@ async fn shutdown_signal() {
 
 #[tokio::main]
 async fn main() {
-    let logger = tracing_logstash::Layer::default();
+    let logger = tracing_logstash::Layer::default()
+        .event_format(tracing_logstash::logstash::LogstashFormat::default()
+            .with_constants(vec![
+                ("service.name", "tracing-logstash".to_owned()),
+                ("service.environment", "development".to_owned()),
+            ])
+        );
 
     let env_filter = EnvFilter::try_from_default_env()
         .or_else(|_| EnvFilter::try_new("info"))
diff --git a/tracing-logstash/src/logstash.rs b/tracing-logstash/src/logstash.rs
index 3b1e74d..46053cb 100644
--- a/tracing-logstash/src/logstash.rs
+++ b/tracing-logstash/src/logstash.rs
@@ -25,6 +25,7 @@ pub struct LogstashFormat<SF = DefaultSpanFormat> {
     display_stack_trace: Option<(DisplayLevelFilter, DisplayLevelFilter)>,
     span_format: SF,
     span_fields: Arc<FieldConfig>,
+    constants: Vec<(&'static str, String)>,
 }
 
 const fn level_value(level: &Level) -> u64 {
@@ -89,12 +90,18 @@ impl<SF> LogstashFormat<SF> {
             ..self
         }
     }
+
     pub fn with_span_fields(self, span_fields: Vec<FieldSpec>) -> Self {
         Self {
             span_fields: Arc::new(FieldConfig::new(span_fields)),
             ..self
         }
     }
+
+    pub fn with_constants(self, constants: Vec<(&'static str, String)>) -> Self {
+        Self { constants, ..self }
+    }
+
     pub fn span_format<FS2>(self, span_format: FS2) -> LogstashFormat<FS2> {
         LogstashFormat {
             display_version: self.display_version,
@@ -107,6 +114,7 @@ impl<SF> LogstashFormat<SF> {
             display_span_list: self.display_span_list,
             span_format,
             span_fields: self.span_fields,
+            constants: self.constants,
         }
     }
 }
@@ -124,6 +132,7 @@ impl Default for LogstashFormat {
             display_span_list: None,
             span_format: Default::default(),
             span_fields: Default::default(),
+            constants: Default::default(),
         }
     }
 }
@@ -258,6 +267,10 @@ where
             }
         }
 
+        for (key, value) in &self.constants {
+            field_visitor.serialize_field(key, value);
+        }
+
         if let Some(filter) = self.display_span_list {
             field_visitor.serialize_field(
                 "spans",